If jump target is outside of function range, perf is not handling it correctly. Especially when target address is lesser than function start address, target offset will be negative. But, target address declared to be unsigned, converts negative number into 2's complement. See below example. Here target of 'jumpq' instruction at 34cf8 is 34ac0 which is lesser than function start address(34cf0). 34ac0 - 34cf0 = -0x230 = 0xfffffffffffffdd0 Objdump output: 0000000000034cf0 <__sigaction>: __GI___sigaction(): 34cf0: lea -0x20(%rdi),%eax 34cf3: cmp -bashx1,%eax 34cf6: jbe 34d00 <__sigaction+0x10> 34cf8: jmpq 34ac0 <__GI___libc_sigaction> 34cfd: nopl (%rax) 34d00: mov 0x386161(%rip),%rax # 3bae68 <_DYNAMIC+0x2e8> 34d07: movl -bashx16,%fs:(%rax) 34d0e: mov -bashxffffffff,%eax 34d13: retq perf annotate before applying patch: __GI___sigaction /usr/lib64/libc-2.22.so lea -0x20(%rdi),%eax cmp -bashx1,%eax v jbe 10 v jmpq fffffffffffffdd0 nop 10: mov _DYNAMIC+0x2e8,%rax movl -bashx16,%fs:(%rax) mov -bashxffffffff,%eax retq perf annotate after applying patch: __GI___sigaction /usr/lib64/libc-2.22.so lea -0x20(%rdi),%eax cmp -bashx1,%eax v jbe 10 ^ jmpq 34ac0 <__GI___libc_sigaction> nop 10: mov _DYNAMIC+0x2e8,%rax movl -bashx16,%fs:(%rax) mov -bashxffffffff,%eax retq Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Chris Riyder <chris.ryder@arm.com> Cc: Kim Phillips <kim.phillips@arm.com> Cc: Markus Trippelsdorf <markus@trippelsdorf.de> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Taeung Song <treeze.taeung@gmail.com> Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/1480953407-7605-3-git-send-email-ravi.bangoria@linux.vnet.ibm.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
||
---|---|---|
Documentation | ||
arch | ||
block | ||
certs | ||
crypto | ||
drivers | ||
firmware | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.cocciconfig | ||
.get_maintainer.ignore | ||
.gitattributes | ||
.gitignore | ||
.mailmap | ||
COPYING | ||
CREDITS | ||
Kbuild | ||
Kconfig | ||
MAINTAINERS | ||
Makefile | ||
README |
README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.